// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2014 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_SPARSESOLVERBASE_H
#define EIGEN_SPARSESOLVERBASE_H

namespace Eigen {

namespace internal {

    /** \internal
  * Helper functions to solve with a sparse right-hand-side and result.
  * The rhs is decomposed into small vertical panels which are solved through dense temporaries.
  */
    template <typename Decomposition, typename Rhs, typename Dest>
    typename enable_if<Rhs::ColsAtCompileTime != 1 && Dest::ColsAtCompileTime != 1>::type
    solve_sparse_through_dense_panels(const Decomposition& dec, const Rhs& rhs, Dest& dest)
    {
        EIGEN_STATIC_ASSERT((Dest::Flags & RowMajorBit) == 0, THIS_METHOD_IS_ONLY_FOR_COLUMN_MAJOR_MATRICES);
        typedef typename Dest::Scalar DestScalar;
        // we process the sparse rhs per block of NbColsAtOnce columns temporarily stored into a dense matrix.
        static const Index NbColsAtOnce = 4;
        Index rhsCols = rhs.cols();
        Index size = rhs.rows();
        // the temporary matrices do not need more columns than NbColsAtOnce:
        Index tmpCols = (std::min)(rhsCols, NbColsAtOnce);
        Eigen::Matrix<DestScalar, Dynamic, Dynamic> tmp(size, tmpCols);
        Eigen::Matrix<DestScalar, Dynamic, Dynamic> tmpX(size, tmpCols);
        for (Index k = 0; k < rhsCols; k += NbColsAtOnce)
        {
            Index actualCols = std::min<Index>(rhsCols - k, NbColsAtOnce);
            tmp.leftCols(actualCols) = rhs.middleCols(k, actualCols);
            tmpX.leftCols(actualCols) = dec.solve(tmp.leftCols(actualCols));
            dest.middleCols(k, actualCols) = tmpX.leftCols(actualCols).sparseView();
        }
    }

    // Overload for vector as rhs
    template <typename Decomposition, typename Rhs, typename Dest>
    typename enable_if<Rhs::ColsAtCompileTime == 1 || Dest::ColsAtCompileTime == 1>::type
    solve_sparse_through_dense_panels(const Decomposition& dec, const Rhs& rhs, Dest& dest)
    {
        typedef typename Dest::Scalar DestScalar;
        Index size = rhs.rows();
        Eigen::Matrix<DestScalar, Dynamic, 1> rhs_dense(rhs);
        Eigen::Matrix<DestScalar, Dynamic, 1> dest_dense(size);
        dest_dense = dec.solve(rhs_dense);
        dest = dest_dense.sparseView();
    }

}  // end namespace internal

/** \class SparseSolverBase
  * \ingroup SparseCore_Module
  * \brief A base class for sparse solvers
  *
  * \tparam Derived the actual type of the solver.
  *
  */
template <typename Derived> class SparseSolverBase : internal::noncopyable
{
public:
    /** Default constructor */
    SparseSolverBase() : m_isInitialized(false) {}

    ~SparseSolverBase() {}

    Derived& derived() { return *static_cast<Derived*>(this); }
    const Derived& derived() const { return *static_cast<const Derived*>(this); }

    /** \returns an expression of the solution x of \f$ A x = b \f$ using the current decomposition of A.
      *
      * \sa compute()
      */
    template <typename Rhs> inline const Solve<Derived, Rhs> solve(const MatrixBase<Rhs>& b) const
    {
        eigen_assert(m_isInitialized && "Solver is not initialized.");
        eigen_assert(derived().rows() == b.rows() && "solve(): invalid number of rows of the right hand side matrix b");
        return Solve<Derived, Rhs>(derived(), b.derived());
    }

    /** \returns an expression of the solution x of \f$ A x = b \f$ using the current decomposition of A.
      *
      * \sa compute()
      */
    template <typename Rhs> inline const Solve<Derived, Rhs> solve(const SparseMatrixBase<Rhs>& b) const
    {
        eigen_assert(m_isInitialized && "Solver is not initialized.");
        eigen_assert(derived().rows() == b.rows() && "solve(): invalid number of rows of the right hand side matrix b");
        return Solve<Derived, Rhs>(derived(), b.derived());
    }

#ifndef EIGEN_PARSED_BY_DOXYGEN
    /** \internal default implementation of solving with a sparse rhs */
    template <typename Rhs, typename Dest> void _solve_impl(const SparseMatrixBase<Rhs>& b, SparseMatrixBase<Dest>& dest) const
    {
        internal::solve_sparse_through_dense_panels(derived(), b.derived(), dest.derived());
    }
#endif  // EIGEN_PARSED_BY_DOXYGEN

protected:
    mutable bool m_isInitialized;
};

}  // end namespace Eigen

#endif  // EIGEN_SPARSESOLVERBASE_H
